Effect of Zn and sucrose supply on grain Zn, Fe and protein contents within wheat spike under detached-ear culture

Wheat (Triticum aestivum L.) is one of most widely consumed cereal crops globally. More than two billion people are affected by nutritional deficiencies caused by zinc (Zn) and iron (Fe) deficiency. Therefore, biofortification is a strategy supposed to be economical, sustainable and easily implemented to increase the micronutrient content in the crops. However, micronutrient distribution, especially Zn and Fe, within the spike has been rarely reported. For this, different concentrations of Zn (0, 30, 60, 90 and 120 mu mol L-1) and sucrose (2%, 4%, 6%) were supplied at Zn concentrations of 30 and 90 mu mol L-1 under detached-ear culture. The results showed that grain weight and grain Zn, Fe and protein contents were higher in superior grains than in inferior grains, and higher in central spikelets than in basal and apical spikelets. Zn supply significantly improved grain Zn, Fe and protein content. Increasing sucrose concentration at low and high Zn supply levels significantly increased grain weight, and grain Zn, Fe and protein contents. The percentage increase in dry weight and nutrient contents of superior and inferior grains was higher in central spikelets than in apical and basal spikelets. It is concluded that grain position significantly affected the grain weight and nutrient content, and these effects could be improved by application of Zn and sucrose. These findings suggest Zn and sucrose application for increasing mineral nutrients contents in wheat grain, and mechanisms of nutrient accumulation in relation to external sucrose and Zn supply should be elucidated in the future.